Recent electronic apparatuses have been made smaller and light weight in addition to developments in the applicability to high-frequency signals and digitized devices, and along with these developments, there have been demands for small-size devices, a high-density packaging property and the like in printed circuit boards being installed in the electronic apparatuses.
There is a rigid flex printed circuit board satisfying these demands which includes a rigid portion and a flex portion (for example, Japanese Patent Application Laid Open Publication No. 2002-158445).
With reference to FIGS. 1A to 2B, a manufacturing process of a conventional rigid flex printed circuit board will be described bellow. FIGS. 1A to 1D are flow charts that show manufacturing processes of the rigid flex printed circuit board. FIG. 2A is a perspective view that shows the substrate and the like shown in FIGS. 1A and 1B and FIG. 2B is a perspective view of a rigid flex wiring board shown in FIG. 1D.
As shown in FIG. 1A, wiring circuits 104 are formed by a subtractive method on both of the surfaces of a flex substrate 101 made of a polyimide film, both of the surfaces of an inner-layer rigid substrate 102 made from a prepreg and the like, and one surface of an outer layer rigid substrate 103.
Substantially, as shown in FIG. 1A and FIG. 2A, flex-portion exposing holes 109 are formed through a bonding sheet 105, the inner-layer rigid substrate 102 and the outer-layer rigid substrate 103, by using a press-punching process and the like. Next, a flex-substrate-use cover layer 106, the inner-layer rigid substrate 102, the bonding sheet 105 and the outer-layer rigid substrate 103 are superposed and placed on the surface and rear surface of the flex substrate 101, and subjected to a laminating process to prepare a laminated member 100 shown in FIG. 1B. In this case, as shown in FIG. 2A, a peripheral portion of a portion (for example, indicated by 103a) that forms a circuit board upon completion of the processes is punched out so that the portion (for example, 103a) to form the circuit board is joined to a frame member (for example, 103b) by using a micro-joint (for example, 103c).
Next, as shown in FIG. 1C, the laminated member 100 is subjected to a drilling process, a plating process and etching so that a through hole 107, an outer-layer wiring circuit 108 and the like are formed therein.
Lastly, the micro-joints (for example, 103c), which have joined a rigid portion B and a flex portion A to the frame member (for example, 103b), are simultaneously punched out by using a die so that a rigid flex printed circuit board 110, shown in FIGS. 1D and 2B, is obtained. In this case, the frame member (for example, 103b) for the substrates 101, 102 and 103 and portions that have been punched out so as to form the substrates 101 are disposed.
Moreover, those circuit boards having an arrangement in which a built-up layer is formed on the surface layer of the rigid flex printed circuit board, and interlayer-connected thereto through IVHS (Interstitial Via Holes) and SVHS (Surface Via Holes) have also been proposed.